1. Field of the Invention
The present invention relates to a method of, and an apparatus for, joining a powder metal blank to a pin. More particularly, the present invention relates to a method of, and an apparatus for, joining a pin to a cover blank for use as an inlet cover of a fuel pump of an internal combustion engine.
2. Discussion of the Related Art
A joined disk-shaped blank and pin are known to be used in an intake chamber of an automotive fuel pump. The inlet cover has a pin on which a gerotor gear assembly is mounted. Thus, if the pin is not joined to the blank in an exact perpendicular relationship with respect to a central plane of the blank, heat will build up during the actuation of the pump because of friction and the motor will require more current to actuate the pump. In addition, reduced perpendicularity creates unacceptable noise and vibration.
A conventional method of making the joined blank and pin includes first separately making the blank and pin. Thereafter, the blank's two end face surfaces are lapped so that they are flat. A center hole is then accurately bored into the blank. The pin is then press fit to the blank in a separate conventional press fitting operation. A drawback of this method is that the degree of precision of the connection between the pin and the blank is not very high. As pointed out above, the pin should be perpendicular with respect to the flat planar surfaces of the blank. However, due to the low precision of the conventional manufacturing method, the pin is frequently not joined exactly perpendicular to the surface of the blank causing, inter alia, the pin to wear prematurely, reduced torque efficiency, excess noise during the operation of the fuel pump and the use of a larger amount of energy than is necessary to actuate the pump. In addition, the prior method is time consuming and costly because of the many steps required.